The present invention relates to a laser process machine suitable for a hole forming machine using a laser, which machine is developed for mainly processing ink discharge orifices in an ink-jet head.
Holes having a predetermined shape and size are formed in a work, or workpiece using a laser beam in consideration of high process precision of the laser beam. In particular, the process precision of ink discharge orifices of an ink-jet head used in a printer, connected to a computer or a wordprocessor, for printing (recording) data by discharging an ink in a predetermined pattern directly influences an ink discharge amount, a discharge direction, and the like. For this reason, the holes must be processed very carefully.
The above-mentioned ink-jet head is employed especially in a bubble-jet type recording head for discharging an ink by utilizing heat energy, of ink-jet recording methods. A typical arrangement and principle of a bubble-jet type recording apparatus are disclosed in, e.g., U.S. Pat. Nos. 4,723,129, 4,740,796, and the like, and can be applied to either of a so-called on-demand type or continuous type An on-demand type bubble-jet recording method will be exemplified below. Electro-thermal converters are arranged in correspondence with a sheet or a liquid channel, which holds a liquid (ink), and are caused to generate heat energy according to drive signals, thus causing film boiling on a heat application surface of a recording head. Consequently, bubbles having a one-to-one correspondence with the drive signals are formed in the liquid (ink), and the liquid (ink) is discharged in the form of liquid droplets from discharge orifices by growth and contraction of the bubbles.
The drive signal to be applied is preferably a pulse signal, as disclosed in U.S. Pat. Nos. 4,463,359 and 4,345,262. As for a temperature rise rate of the heat application surface, conditions disclosed in U.S. Pat. No. 4,313,124 are preferably employed.
The ink-jet head is constituted by a combination of discharge orifices, a liquid channel (a linear liquid channel or a right-angled liquid channel), and electro-thermal converters. In addition to this arrangement, a heat application portion may be arranged on a bent region, as disclosed in, e.g., U.S. Pat. Nos. 4,558,333 and 4,459,600. Furthermore, the ink-jet head may be arranged as follows. That is, a slit common to a plurality of electro-thermal converters may be used as a discharge portion of the electro-thermal converters, as disclosed in, e.g., Japanese Patent Laid-Open No. 59-123670, or holes for absorbing output waves of heat energy may be formed in correspondence with a discharge portion, as disclosed in, e.g., Japanese Patent Laid-Open No. 59-138461. Note that each recording head described in the above-mentioned specifications assures a length corresponding to a predetermined width by combining a plurality of recording heads. However, a single recording head may have a length corresponding to the predetermined width (the width of a maximum recording medium, which can be used in recording of a recording apparatus).
The ink-jet head may be arranged as a chip type head, which is attached to an apparatus main body to attain electrical connections (for electro-thermal converters), and to be able to be supplied with an ink, or as a cartridge type head provided to a recording head itself.
As a process method of forming the ink-jet head, which can be used in various forms, a laser process apparatus for radiating laser light onto a work through a mask formed with holes each having a predetermined shape is proposed. With this apparatus, laser light is radiated on a mask formed with a plurality of arrays of holes so as to project laser beam spots similar to the holes formed in this mask onto a work to be processed, thereby forming holes in the work.
This mask is arranged to be able to finely adjust its positions in the height and lateral directions, so that laser light to be radiated includes all the holes of the mask. The position adjustment is manually performed, and the adjustment result is visually confirmed. The laser light intensity varies depending on radiation positions. For this reason, even when laser light is radiated through holes having the same shape, holes formed in the work undesirably have different shapes depending on the beam radiation positions. Therefore, the position adjustment of the mask is performed by actually processing a work, and confirming the states of formed holes.
However, the above-mentioned conventional laser process apparatus suffers from the following problems, and its improvement is desired.
(1) When laser light is focused at one point to form a hole one by one, a very long time is required for processing a work, which requires formation of a large number of holes, resulting in poor work efficiency.
(2) Especially, a very long time is spent to set accurate hole formation positions on a work, thus considerably impairing the work efficiency.
(3) The size of each hole is largely influenced by laser light intensity. Since laser light emitted from an excimer laser has a nonuniform energy distribution, when a plurality of holes are simultaneously formed by projecting a plurality of laser beams which are divided from a laser light emitted from a laser source whereby the laser light is radiated on the mask on which a plurality of holes are formed, the holes cannot have a uniform size. As a result, holes having a desired shape cannot be formed.
(4) In order to form a hole having a large hole area without changing the materials and shapes of a mask and a work, the energy density of laser light to be radiated on a work W must be increased.
In recent years, very high precision, i.e., precision on the order of microns, is required in a laser process. According to this requirement, very small holes must be formed in a mask. As a result, a work and a mask must be precisely aligned with each other.
The mask must be exchanged when a work shape is altered or when the mask itself is deteriorated. When the mask is exchanged, aligning operations between a work and a mask are performed. These aligning operations are performed as follows. That is, a work as a dummy is processed, and the shape of the processed portion is photographed using an industrial television. A measurement value of a predetermined portion obtained based on image information as the photographing result is compared with a predetermined setting value.
For this reason, the following problems are pointed out.
(5) In a conventional laser process apparatus, when a mask is exchanged, a work is actually processed, and the mask position is checked based on the shape of the processed hole. For this reason, the adjustment of the mask position requires much time, resulting in poor productivity.
(6) A mask is aligned using image information obtained using the industrial television. However, since the industrial television has a very narrow field angle, much time is required to bring a processed portion within an image region. As a result, a very long time is required for the manufacture, which leads to an increase in manufacturing cost.
In the above-mentioned laser hole forming process machine, a mask, which is formed of, e.g., Ni, and comprises a mask pattern for converting laser light emitted from a laser light source into light beams corresponding to holes to be formed, is fixed to a mask holder arranged on the laser optical axis between the laser light source and a work in which holes are to be formed. The light beams passing through the mask pattern of the mask are radiated on a process surface of a work to form holes.
In this laser hole forming process machine, light passing through the mask pattern is 1% or less of the entire laser light, and most laser light is reflected or absorbed by the mask. As a result, the absorbed laser light is converted to heat, and the heat causes a temperature rise of the mask. For this reason, the mask holder is attached to an apparatus frame, and the temperature rise of the mask is suppressed by natural cooling.
However, since the temperature rise of the mask is suppressed by natural cooling in this manner, the following problems are posed.
(7) When the atmospheric temperature (i.e., room temperature) around the mask is increased, the mask temperature is undesirably increased.
(8) When the temperature rise occurs due to laser light radiation, the cooling effect of the mask cannot be expected. As a result, the mask is expanded, and the mask pattern is deteriorated, thus impairing process precision.
For example, assume that Ni is used as a mask material, as described above. The linear expansion coefficient of Ni is 1.3.times.10.sup.-5. In order to suppress the pitch precision of processed holes within a range of .+-.1 .mu.m/8.2 mm, a change in temperature of the mask must be controlled to fall within a range of .+-.10 degrees. However, in consideration of a change in room temperature, and the temperature rise caused by radiation of a laser beam, it is difficult to control a change in temperature of the mask to fall within a range of .+-.10 degrees by natural cooling.